1. Field of the Invention
This invention relates to an exhaust gas analysis system for motor vehicles, and particularly to an improved system for specifying the amount of a particular exhaust gas contaminant relative to the surrounding atmosphere. The system is specifically adapted to simultaneously measure the concentration of carbon monoxide (CO) and a hydrocarbon component (HC), such as hexane, in the exhaust gas.
2. Description of the Prior Art
Due to the recent public interest in reducing environmental pollution, particularly that caused by emissions from the exhaust systems of motor vehicles, a number of systems have been developed for measuring the amount of selected contaminants in the exhaust gas emissions of vehicles. Many of the systems are highly inaccurate and cannot be used reliably. Other systems require continuous adjustment to provide accuracy, the adjustments taking the form of zeroing the system before each test, or adjusting the range of output signals, i.e., span adjustment, depending on the concentration of the measured contaminants. The necessity for continuous adjustment leads to inconvenience and possible inaccuracies, and further reduces the number of emissions tests which can be made over a selected time interval.